In the semiconductor device manufacturing process, for example, a photolithography is performed in which various processings such as, e.g., a resist application processing to apply a resist liquid on a semiconductor wafer (hereinafter, referred to as “wafer”) forming a resist film, an exposure processing to expose a predetermined pattern formed on the resist film, and a developing processing to develop the exposed resist film, are sequentially performed so that a predetermined resist pattern is formed on the wafer. Then, an etching processing of a film to be processed formed on the wafer is performed using the resist pattern as a mask, and then, for example, a removal processing of the resist film is performed so that the predetermined pattern is formed on the film to be processed.
In recent years, when forming a pattern of a film to be processed as described above, the pattern of the film to be processed has been required to be narrowed in order to ensure a higher integration of a semiconductor device. As a result, several methods have been developed including, for example, shortening the wavelength of the light used for an exposure processing. However, the method of forming a fine pattern of a film with, for example, a several-nanometer-order scale is facing a difficult situation due to the technical difficulties and cost limitations.
Therefore, it has been proposed to use a side wall transfer (“SWT”) method which is one of so-called double patterning methods in which, for example, a silicon oxide film (SiO2 film) is used as a sacrifice film and a mask is formed on the opposite lateral wall sections of a resist pattern. In the SWT method, a film is patterned in a pitch finer than the pitch of the resist pattern formed on a wafer by initially performing a photolithography processing. That is, in this method, a silicon oxide film is formed first on a resist pattern under a temperature environment of, for example, no more than 300° C. and the silicon oxide film is etched such that the silicon dioxide film remains only on the lateral wall sections of the resist pattern. Then, the resist pattern is removed and a silicon oxide film pattern is formed on the film to be processed of the wafer. The film to be processed is then etched using the fine pattern of the silicon oxide film formed in such a manner as a mask to form a fine pattern of the film to be processed on the wafer (Patent Document 1).